From a8236c96a8f8482ba511d03e0f5141b1b19721ee Mon Sep 17 00:00:00 2001
From: Trevor Spreadbury <trevorspreadbury@gmail.com>
Date: Wed, 20 Jul 2022 00:45:32 -0500
Subject: [PATCH 1/2] Create a RepoProvider that uses an API to proxy another
 RepoProvider

ProxyRepoProvider queries an API endpoint on instantiation with
the provided 'spec' as the resource id. The API must return both
a 'provider' and an updated 'spec'. Attributes are then copied from
the proper RepoProvider. The initializatin returns the proper
RepoProvider and updated kwargs
---
 binderhub/app.py           |  2 ++
 binderhub/main.py          |  1 +
 binderhub/repoproviders.py | 70 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+)

diff --git a/binderhub/app.py b/binderhub/app.py
index 47198e60c..61de947f4 100644
--- a/binderhub/app.py
+++ b/binderhub/app.py
@@ -62,6 +62,7 @@
     HydroshareProvider,
     RepoProvider,
     ZenodoProvider,
+    ProxyRepoProvider
 )
 from .utils import ByteSpecification, url_path_join
 
@@ -517,6 +518,7 @@ def _default_build_namespace(self):
             "figshare": FigshareProvider,
             "hydroshare": HydroshareProvider,
             "dataverse": DataverseProvider,
+            "proxy": ProxyRepoProvider,
         },
         config=True,
         help="""
diff --git a/binderhub/main.py b/binderhub/main.py
index 6d302972e..d2a3bf27d 100644
--- a/binderhub/main.py
+++ b/binderhub/main.py
@@ -21,6 +21,7 @@
     "figshare": "Figshare",
     "hydroshare": "Hydroshare",
     "dataverse": "Dataverse",
+    "proxy": "Proxy"
 }
 
 
diff --git a/binderhub/repoproviders.py b/binderhub/repoproviders.py
index 256d4985d..786180bfd 100644
--- a/binderhub/repoproviders.py
+++ b/binderhub/repoproviders.py
@@ -1036,3 +1036,73 @@ async def get_resolved_spec(self):
 
     def get_build_slug(self):
         return self.gist_id
+
+class ProxyRepoProvider(RepoProvider):
+    """RepoProvider that acts as a proxy for another provider
+    
+    Uses an external API to determine desired provider and spec given
+    an input spec that acts as a repo id in the external API."""
+
+    name = Unicode("Proxy")
+
+    display_name = "Proxy"
+
+    api_url = Unicode(
+        config=True,
+        help="""The path to the external API
+        Requests to api_url/spec should return a json with a spec
+        field and a provider field that maps to one of the predefined
+        repoproviders.
+        """
+    )
+
+    labels = {
+        "text": "URL to API endpoint returning project's spec and provider",
+        "tag_text": "Git ref (branch, tag, or commit)",
+        "ref_prop_disabled": True,
+        "label_prop_disabled": True,
+    }
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.provider, kwargs = self.resolve_provider(kwargs)
+        import inspect
+        for name, value in inspect.getmembers(self.provider(*args, **kwargs)):
+            if name in ["__dict__", "labels"]:
+                continue
+            try:
+                setattr(self, name, value)
+            except Exception as e:
+                self.log.debug(f"Error copying {e}")
+        self.log.debug(f"Copied attributes from {self.provider} instance")
+
+    def resolve_provider(self, kwargs):
+        import requests
+        spec = kwargs["spec"]
+        # remove auto generated commit
+        spec = spec.split("/")[0]
+        project_url = f"{self.api_url}/{spec}"
+        self.log.debug(f"Fetching {project_url}")
+        project_metadata = requests.get(project_url).json()
+        try:
+            provider = project_metadata["provider"]
+            spec = project_metadata["spec"]
+        except AttributeError as e:
+            msg = f"""API endpoint {project_url} must return json with
+                      'provider' and 'spec' attributes"""
+            raise ValueError(msg)
+        providers = {
+            'gh': GitHubRepoProvider,
+            'gist': GistRepoProvider,
+            'git': GitRepoProvider,
+            'gl': GitLabRepoProvider,
+            'zenodo': ZenodoProvider,
+            'figshare': FigshareProvider,
+            'hydroshare': HydroshareProvider,
+            'dataverse': DataverseProvider,
+        }
+        provider_class = providers[provider]
+        self.log.debug(f"Using {provider} provider with spec {spec}")
+        kwargs["spec"] = spec
+
+        return provider_class, kwargs
\ No newline at end of file

From 34312f87abd230d074f94615d12d04cfa46d4911 Mon Sep 17 00:00:00 2001
From: Trevor Spreadbury <trevorspreadbury@gmail.com>
Date: Thu, 21 Jul 2022 08:21:48 -0500
Subject: [PATCH 2/2] add new provider prefix to ui, index javascript

---
 binderhub/event-schemas/launch.json | 3 ++-
 binderhub/static/js/index.js        | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/binderhub/event-schemas/launch.json b/binderhub/event-schemas/launch.json
index 16e277cf4..7323d8ace 100644
--- a/binderhub/event-schemas/launch.json
+++ b/binderhub/event-schemas/launch.json
@@ -14,7 +14,8 @@
         "Zenodo",
         "Figshare",
         "Hydroshare",
-        "Dataverse"
+        "Dataverse",
+        "Proxy"
       ],
       "description": "Provider for the repository being launched"
     },
diff --git a/binderhub/static/js/index.js b/binderhub/static/js/index.js
index 6d2673500..d85646034 100644
--- a/binderhub/static/js/index.js
+++ b/binderhub/static/js/index.js
@@ -114,7 +114,7 @@ function getBuildFormValues() {
 
   let ref = $('#ref').val().trim() || $("#ref").attr("placeholder");
   if (providerPrefix === 'zenodo' || providerPrefix === 'figshare' || providerPrefix === 'dataverse' ||
-      providerPrefix === 'hydroshare') {
+      providerPrefix === 'hydroshare' || providerPrefix === 'proxy') {
     ref = "";
   }
   const path = $('#filepath').val().trim();